The present invention relates generally to methods of coloring hair and more particularly to lightening the natural color of the hair while simultaneously imparting one or more shades which complement the lightened natural hair color.
Coloring hair as an act of adornment by men and women exists in most civilizations. It is estimated that 30-40% of the women in industrialized nations color their hair either in the home using commercially available home hair coloring products or at a salon by a professional hairdresser.
Various systems for coloring hair exist. Temporary hair colorings are those which last generally until the first shampoo. The colors employed, often referred to as fugitive colors, are typically of a higher molecular weight and are incapable of penetrating the cortex of the hair and consequently are externally deposited on the hair.
Temporary hair dyes are generally basic dyes, acid dyes, disperse dyes, pigments or metallized dyes, belonging to various chemical classes including azo, anthraquinone, triphenylmethane, phenazinic, xanthenic, and benzoquinoneimine.
Semi-permanent hair coloring is resistant to several shampooings. The colors employed are typically direct dyes of low molecular weight and capable of penetrating the cortex of the hair. Semi-permanent hair colorings belong generally to the chemical classes of nitrophenylenediamines, nitroaminophenols and aminoanthraquinones.
Semi-permanent hair dyes are particularly important because they provide a range of hair shades impossible to obtain with the oxidation dyes employed in permanent hair colorings.
Permanent hair colorings are those that are resistant to shampooing, brushing, friction, light, etc. The oxidation dyes, or para-dyes, used in permanent hair coloring are colorless until oxidized by an oxidizing agent, typically hydrogen peroxide or a derivative.
In addition to acting as an oxidizing agent, hydrogen peroxide is also important in its ability to solubilize the natural melanin pigments of the hair, consequently bleaching or lightening the hair. Thus, hair can be lightened, for example, to provide a blonde shade by employing hydrogen peroxide to first remove natural pigments, and then to impart a new color to the lightened hair with oxidation dyes. Typically, a combined bleach and oxidation dye will be employed to bleach the hair while the dyes are penetrating. This method allows dark hair to be lightened by several shades while giving the appearance of not having been bleached.
Hydrogen peroxide has also been employed in combination with a 1:2 chromium complex of a mono azo dye and in combination with a dye derived from triarylmethane to lighten and tint hair. These types of dyes are generally classed as temporary hair dyes as discussed above.
Although the above methods are adequate to provide effective hair coloring, they have several disadvantages. Only the permanent oxidation dyes will provide lasting results. However, even so-called permanent oxidation dyes will leach out over a relatively short period of time, e.g., over a period of one to twelve weeks depending on the number of shampooings, the condition of the hair, etc. Color setting lotions, for example, the 1:2 chromium complex of a a mono azo dye discussed above, must generally be applied weekly to maintain the desired color. For more permanent colors, the length of time between treatments is upwards to a month. However, when hydrogen peroxide is employed, especially in color setting lotions employed to lighten and impart shading to hair at the same time, the frequent application of hydrogen peroxide can severely damage the hair. In the case of oxidation dyes, unwanted tones resulting from the treatment cannot be corrected without adding additional harmful hydrogen peroxide, which undesirably further lightens the hair.
Additionally, there is an added risk in using oxidation dyes due to skin irritation or sensitization and systemic toxicity. For example, the common oxidation dye components p-phenylenediamine and p-toluylenediamine, are capable of causing contact dermatitis.
Aside from the temporary results, complications and risks of the traditional hair dying techniques mentioned above, hair colorists have strived to improve their ability to add color and shades to hair. One desire is to duplicate as closely as possible the color and shadings, or highlights, achieved by the action of sunlight on the hair. Heretofore, a method of achieving effects much like the natural effects of sunlight through a hair coloring process that not only attained the desired results, but avoided the temporary nature of many techniques, or the excessive and prolonged use of hydrogen peroxide and potentially harmful oxidation dyes, has not been known.